Fast Ionospheric Correction Algorithm for Galileo Single Frequency Users

Abstract

We propose an alternative ionospheric correction approach for single frequency Galileo users. In the proposed approach the broadcasted coefficients are used to drive the Neustrelitz Total Electron Content (TEC) Model (NTCM) instead of the standard Galileo ionosphere model NeQuick-G. The NTCM-based correction approach uses 12 model coefficients, the solar radio flux index F10 and a few empirically fixed parameters. The required TEC values can be computed at any location and time without using any spatial or temporal interpolation of parameters. This makes NTCM very fast running in operational applications. The presented approach performs well when fed with the same Az parameter as NeQuick-G. The global performance analysis with reference Vertical Total Electron Content (VTEC) data from the International GNSS Service (IGS) shows that the performance of the NTCM was better than that of NeQuick-G. A comparison with reference Slant TEC (STEC) data shows that there is no significant difference between both models performance in terms of residual statistics such as Root Mean Square (RMS), mean and Standard Deviation (STD). Here, an improved mapping function could even reduce corresponding errors when transforming NTCM derived VTEC to STEC values used for comparison. When comparing the computational time, it is found that the NTCM use is in average 65 times faster than the NeQuick-G operation.